Before you can answer this question, you must know what an dependent variable is. The dependent variable is the one aspect of the experiment that is measured to see if there is a relationship between it and the independent variable. Knowing that, you might have chosen one of two things that Alex could use as a dependent variable. Alex could wait a predetermined time period and then measure the length of the worms or he could measure how long it takes the worms to reach a predetermined length. Here is what your answer should look like:
Possibility A: Alex could use the length of the worms as his dependent variable. He can grow several groups of worms at different temperatures for a predetermined period of time and measure to see which ones got the longest. I believe this is correct because measuring length to see if there is a relationship to temperature fits the requirements of the dependent variable in an experiment.
Possibility B: Alex could use the time period it takes for the worms to reach the ideal length as his dependent variable. He can grow several groups of worms at different temperatures and time how long it takes for them to reach a predetermined length. I believe this is correct because measuring the time it takes to reach a predetermined length fits the requirements of the dependent variable in an experiment.
Regardless of which dependent variable you choose, you must keep in mind that all good experiment designs can only include one dependent variable. Therefore, Alex cannot measure both time and length in the same
experiment.
Possibility A: Alex could use the length of the worms as his dependent variable. He can grow several groups of worms at different temperatures for a predetermined period of time and measure to see which ones got the longest. I believe this is correct because measuring length to see if there is a relationship to temperature fits the requirements of the dependent variable in an experiment.
Possibility B: Alex could use the time period it takes for the worms to reach the ideal length as his dependent variable. He can grow several groups of worms at different temperatures and time how long it takes for them to reach a predetermined length. I believe this is correct because measuring the time it takes to reach a predetermined length fits the requirements of the dependent variable in an experiment.
Regardless of which dependent variable you choose, you must keep in mind that all good experiment designs can only include one dependent variable. Therefore, Alex cannot measure both time and length in the same
experiment.